Water in oil emulsions containing anisole

ABSTRACT

Improvements in the rate of stripping of benzyl alcohol containing water-in-oil emulsions by incorporating in the organic phase thereof an effective amount of anisole.

FIELD OF THE INVENTION

The present invention relates to improvements in the stripping rate ofpaint stripping formulations comprising water-in-oil emulsionscontaining benzyl alcohol, the improvement resulting from incorporatingin the oil phase thereof an effective amount of anisole.

BACKGROUND OF THE INVENTION

The benzyl alcohol based, water in oil emulsions to which this inventionis directed are described, for example, in U.S. Pat. No. 5,542,986(referred to herein as "the '986 patent") and in copending U.S. patentapplication Ser. Nos. 08/706,850 and 08/707,261 (referred to herein as"the '850 and '261 applications"), the entire specifications of whichare hereby incorporated by reference. Particularly preferred are the waxcontaining water-in-oil emulsions of the '850 and '261 applications.

SUMMARY OF THE INVENTION

In paint stripper formulations containing a water-in-oil emulsion havinga water phase and a continuous benzyl alcohol (oil) phase, animprovement is provided which comprises incorporating anisole in thebenzyl alcohol phase in an amount effective to improve the strippingrate. Preferred embodiments include alkaline strippers where ammonia isincorporated in the emulsion's water phase and acid strippers wherebenzyl formate is incorporated in the emulsion's benzyl alcohol phase.Other preferred embodiments include the incorporation of a terpene suchas d-limonene to retard the rate of water evaporation and/or, in theammonia containing strippers, pyrrole to further enhance the strippingrate.

DETAILED DESCRIPTION OF THE INVENTION

It has now been found that incorporation of anisole into the organic,benzyl alcohol phase of a water-in-oil emulsion enhances the rate ofstripping.

The wax-containing water-in-oil emulsions of the '850 and '261applications are particularly advantageous in paint removers since theemulsions, among other things, reduce odor and the wax (natural orsynthetic) improves the stripping efficiency by retarding evaporation ofingredients such as water and other volatiles that enhance stripping.When wax is present, it is generally used in an amount which is slightlyin excess (1% by weight) of that which would saturate the organic phase.A preferred wax is paraffin wax (which term includes its individualcomponents). Paraffin or mineral oil, vegetable wax, microcrystallinewax, ceresine wax and montan wax may similarly be used.

The anisole is generally used in an amount of from about 1.0 to about24.0 weight %, based on the total weight of the emulsion (preferablyfrom about 2 to about 16%), depending on the substrate to be stripped,the amount of solvents (and wax, if any) in the stripper formulation,and so on. The upper limit is a practical one, since additional anisoleseems to have little effect on the stripping rate, while at lower levelssolvency can be lost.

One or more terpenes can also be added with the anisole, since thepresence of a terpene helps to reduce evaporation of water and othersolvents from these inverse emulsion paint strippers, so that the uselife of such strippers can be extended to 24 hours or more. When usingthis combination, the anisole is preferably used in amounts of about8-16%, while the terpene is preferably used in amounts of about 4-8%.Examples of such terpenes are d-limonene (preferred), dipentene (alsoknown as 1-methyl-4-(1-methylethenyl)-cyclohexene), myrcene,alphapinene, linalool and mixtures thereof.

In alkaline strippers pyrrole can also be added with the anisole toenhance the stripping rate, in which event the total amount of anisoleand pyrrole is from about 1 to about 24% (preferably 2-16%), or with theanisole/-terpene combination. When anisole, terpene(s) and pyrrole areall incorporated in an ammonia-containing stripper, an optimized systemis generally one which has about 8-16% anisole, about 5-9% terpene(s)and about 0.3-8% pyrrole.

The amount of wax incorporated in the emulsion of the preferredstrippers is normally from about 0.02 to about 5.0 percent by weight,based on the total weight of the emulsion, more typically from about 0.1to about 1.0%. Any type of commercially available paraffin wax orceresine wax (or their components) can be used. Most paraffin waxes havea melting point in the range of about 47° to 65° C.

With reference to the '850 and '261 applications and the '986 patent, apaint stripper formulation employing such an emulsion can be made bymixing together water; benzyl alcohol (and, if desired, formic acid, aportion of which reacts with a portion of the benzyl alcohol to form, insitu, some benzyl formate and additional water; alternatively, the sameequilibrium mixture of water, benzyl alcohol, formic acid and benzylformate can be formed by starting with the equilibrium mixture or with acorresponding equivalent amount of benzyl formate, water and,optionally, benzyl alcohol or formic acid if it is desired to have amolar excess of benzyl alcohol or formic acid, respectively); anisole;wax, if any; up to about 2% by weight of thickeners (such as ahydroxypropyl cellulose or methylcellulose); up to about 15% by weightof a hydrocarbon solvent (aromatic or aliphatic, including petroleumdistillates) to help wet the thickener and dissolve any wax; up to about2% by weight of surfactants (such as sodium xylene sulfonate or animidazoline such as oleic hydroxyethyl imidazoline); up to about 15% byweight of ammonia for a formulation on the alkaline side, or sodiumhydroxide if formic acid is present; up to about 5% by weight ofcorrosion inhibitors (such as 2-mercaptobenzotriazole, benzotriazole orsodium silicate); and, if desired, a small amount (usually no more than0.1 to 0.3 grams per gallon) of a dye.

Examples (Nos. 1 to 7) of such paint remover formulations with optimizedamounts of solvents of this invention are as follows (the ingredientamounts being listed in parts by weight), together with a comparativeexample (No. C1) having no anisole:

    ______________________________________                                               Example Nos:                                                                  1    2      3      4    5    6    7    C1                              ______________________________________                                        benzyl alcohol                                                                         40.0   40.0   40.0 40.0 40.0 40.0 40.0 40.0                          hydroxypropyl                                                                          .5     .5     .5   .5   .5   .5   .5   .5                            cellulose*                                                                    aromatic .5     .5     .5   .5   .5   .5   .5   .5                            hydrocarbon                                                                   solvent                                                                       paraffin wax                                                                           .3     .3     .3   .3   .3   .3   .3   .3                            surfactant                                                                             .7     .7     .7   .7   .7   .7   .7   .7                            corrosion                                                                              3.5    3.5    3.5  3.5  3.5  3.5  3.5  3.5                           inhibitors                                                                    ammonia  5.0    5.0    5.0  5.0  5.0  5.0  5.0  5.0                           water    41.5   33.5   25.5 33.5 25.5 29.0 25.5 49.5                          d-limonene                                                                             0      0      8.0  8.0  0    5.5  8.0  0                             anisole  8.0    16.0   16.0 8.0  12.0 11.5 8.0  0                             pyrrole  0      0      0    0    12.0 3.5  8.0  0                             ______________________________________                                         *The amount of hydroxypropyl cellulose thickener was varied between 0.4       and 0.6 to compensate for varying viscosity due to varying amounts of         solvent                                                                  

Comparative stripping tests were run on these formulations in standardperformance tests on aluminum panels painted with a Polyurethane TopcoatSystem (polyurethane topcoat over an epoxy primer) or a PolyurethaneTopcoat/Polyurethane Primer System (polyurethane topcoat over apolyurethane primer). The stripping tests followed MIL-R-81294, amilitary specification used to evaluate the effectiveness of paintstrippers to remove a white polyurethane paint from aluminum. While notests were done on Epoxy Topcoat Systems (epoxy topcoats over epoxyprimers), previous experience has shown that results with PolyurethaneTopcoat Systems are similar to that with Epoxy Topcoat Systems. Theresults of these tests are reported in Table I below, the data showingthe percent of the panels stripped in 24 hours on each of the systems:

                  TABLE I                                                         ______________________________________                                                     % of Panels  % of Panels                                                      Painted with Painted with                                                     Polyurethane/Poly-                                                                         Polyurethane/-                                      Example No.  urethane Stripped                                                                          Epoxy Stripped                                      ______________________________________                                        C1*          0            0                                                   1            25           30                                                   2*          50           22.5                                                3            98           50                                                  4            96           40                                                   5*          35           10                                                  6            100          38                                                  7            100          38                                                  ______________________________________                                         *-These report an average of tests on two separately made formulation         batches                                                                  

Examples 1 and 2 show that anisole alone is effective for improvedstripping on both paint systems. Improved stripping also results fromcombinations of the anisole with a terpene (d-limonene) and/or pyrrole,the combinations containing both anisole and a terpene beingparticularly effective, as is evident from Examples 3-7.

What is claimed is:
 1. In a paint stripper formulation containing awater-in-oil emulsion having a water phase and a continuous benzylalcohol phase, the improvement comprising incorporating anisole andd-limonene in the benzyl alcohol phase in an amount effective toincrease the rate of stripping.
 2. The paint stripper formulation ofclaim 1 wherein the benzyl alcohol phase contains a wax.
 3. The paintstripper formulation of claim 2 wherein the water phase containsammonia.
 4. The paint stripper formulation of claim 2 wherein the benzylalcohol phase contains benzyl formate.
 5. A method of increasing thestripping rate of a water-in-oil emulsion paint stripper which comprisesincorporating into the emulsion's benzyl alcohol phase an effectiveamount of anisole and d-limonene.
 6. The paint stripper formulation ofclaim 3 wherein pyrrole is also incorporated in the benzyl alcoholphase.
 7. A method as in claim 5 wherein a wax is incorporated into theemulsion's benzyl alcohol phase.
 8. A method of increasing the strippingrate of an alkaline water-in-oil emulsion paint stripper which comprisesincorporating into the emulsion's benzyl alcohol phase an effectiveamount of anisole and d-limonene.
 9. A method as in claim 8 wherein awax is also incorporated into the emulsion's benzyl alcohol phase.
 10. Amethod as in claim 9 wherein pyrrole is also incorporated into theemulsion's benzyl alcohol phase.
 11. A method of increasing thestripping rate of an acidic water-in-oil emulsion paint stripper whichcomprises incorporating into the emulsion's benzyl alcohol phase aneffective amount of anisole and d-limonene.
 12. A method as in claim 11wherein a wax is also incorporated into the emulsion's benzyl alcoholphase.